Trigger to update field on Campaign from Campaign Member failing

Hi,

I'm trying to mimic a workflow field update from the Campaign Member to the Campaign (as it cannot be done via a workflow). What I want is when a picklist (Send_tutor_details_to_client__c) is updated to 'First', the contents of another field on the Campaign Member (Tutor_details_for_email__c) are copied to a corresponding field on the Campaign (Tutor_1__c).

I'm getting an error about sObjects, however, that I don't understand.

sObject type 'Interview_Date_Time_Confirmed__c' is not supported. If you are attempting to use a custom object, be sure to append the '__c' after the entity name. Please reference your WSDL or the describe call for the appropriate names.